This invention relates to an engine RPM control device for an outboard motor and more particularly to an improved speed control device for a watercraft and a method for controlling the watercraft speed.
As is well known, it is the normal practice in watercraft to provide an operator throttle control by which the operator may set the throttle speed of the powering engine. Although these throttle controls normally permit the operator to place the throttle in a fixed condition, the actual speed of the watercraft may vary considerably even though the set throttle position maintains constant. As is well known, a wide variety of factors may affect the speed of the watercraft other than throttle position. In order to provide a speed control for a watercraft wherein the watercraft may be maintained at a constant speed without the operator's continuous attention, it has been proposed to provide some form of automatic speed control. Such a speed control device is shown in U.S. Pat. No. 4,566,415, entitled Speed Controller for Marine Propulsion Device, issued Jan. 28, 1986 in the name of Tomio Iwai et al, which patent is assigned to the assignee of this application.
As is shown in that patent, an automatically operated speed control mechanism is provided that cooperates with the engine throttle control for varying the throttle control position so as to maintain a uniform watercraft speed. This is done in the illustrated embodiment of that Patent by means of a controlling motor that operates a cam which, in turn, cooperates with the throttle control mechanism for positioning the throttle control. In one of the illustrated embodiments, the throttle control is provided for an outboard motor and the controlling mechanism is contained within the power head of the motor. Although such an arrangement has the advantages of offering a unitary construction and one which can be easily moved from one watercraft to the other, the extremely compact nature of an outboard motor makes it difficult to incorporate a speed control mechanism within it.
It is, therefore, a principal object of this invention to provide an improved engine speed control device that is particularly adaptable for use with an outboard motor and which is extremely compact.
It is a further object of this invention to provide an improved and compact throttle controller that is adaptable for use with outboard motors.
In connection with automatic speed control mechanisms it is the normal practice to employ some form of logic which compares actual engine speed with desired engine speed and controls the engine speed if there is a variance. These devices normally employ some form of motor or drive for positioning the throttle. However, if there is a malfunction, the drive may continue to operate and position the throttle without the operator's knowledge or desire.
It is, therefor, a further object of this invention to provide a malfunction operator for an automatic speed control.
It is a further object of this invention to provide an automatic speed control for an internal combustion engine that will provide a malfunction indication in the event the speed control operates when it is not intended.